Neurodegenerative processes can involve diverse areas of the Central Nervous System (CNS). Neurodegeneration appears clinically as a breakdown of functionally connected neuronal circuits with corresponding alterations in the neurotransmitter system and morphological organization of the affected cell system.
The normal functioning of the CNS presupposes a well-balanced interaction between different biochemical and structurally linked neuronal systems. When one member of a neuronal circuit is altered in its structural or biochemical entity, an imbalance in the functional system results and a compensatory mechanism must be activated in order to maintain physiological equilibrium.
Perhaps the most severe form of neurodegeneration is that seen after stroke. This form of cerebral ischemia results in the death of neurons, as well as glial cells and vascular elements of the brain. Quite often a stroke results in paralysis, memory loss, inability to communicate, and even death. Reactive oxygen intermediates are believed to play a role in causing brain death in stroke victims. Another form of cerebral ischemia that can be quite devastating to important groups of selectively vulnerable neurons, is global ischemia. Global cerebral ischemia is commonly seen in victims of cardiac arrest during the period of time the heart is undergoing fibrillation. Neuronal death from global ischemia is a common occurrence in heart attack victims that undergo cardiac arrest and cardiac arrest is a common occurrence in heart attack patients. Reactive oxygen species are also believed to be one of the causative factors in neuronal death during the reperfusion phase after global ischemia. Ischemia-reperfusion injury caused by global or local ischemia or during transplantation can also affect other major organs of the body such as the kidney, liver and heart. Reactive oxygen intermediates that are generated during the reperfusion phase in these organs are thought to cause significant injury.
Other degenerative diseases of the central nervous system are believed to be exacerbated or initiated by processes that result in the generation of reactive oxygen intermediates. Parkinson's disease (PD) is characterized by reduced size and velocity of movements. In Alzheimer's disease (AD), cognitive impairment is the cardinal clinical symptom. In motoreuron disease, (for example, amyotrophic lateral sclerosis, ALS), a degeneration of the central pyramidal, the peripheral motor system or both is the reason for the clinical picture.
Idiopathic PD is a movement disorder in which symptomatology is defined by three cardinal symptoms: tremor at rest, rigidity and akinesia (Fahn, 1989). The course of the disease is a progressive one. For a long time, anticholinergic drugs were the only effective treatment of parkinsonian symptoms. The beneficial effect of L-3,4-dihydrophenylalanine (L-DOPA) therapy has increased patient's life expectancy to a significant degree. However, the advanced stage of the disease is dominated by the complications of L-DOPA therapy and lack of L-DOPA responsiveness. A limiting factor in PD therapy is the psychotic potential of many anti-parkinsonian drugs.
ALS is a chronic progressive degenerative disorder, which, in its classical form, appears sporadically. The most prominent pathological change in ALS patients is a loss of large motoreurons in the motor cortex, brain stem and spinal cord.
Cognitive decline is the essential clinical criteria for AD manifested by memory loss, disorientation and the concomitant loss of enjoyment of life associated therewith. Only after death can the diagnosis be confirmed pathologically by the presence of numerous amyloid and neuritic plaques in the brain.
At present, the pharmacological therapy of neurodegenerative disorders is limited to symptomatic treatments that do not alter the course of the underlying disease.
Meanwhile, because of the current dissatisfaction with the currently marketed treatments for the above-described indications within the affected population, the need continues for safer, better-calibrated drugs which will either slow the process of neurodegeneration associated with focal or global ischemia, ALS, Alzheimer's and Parkinson's disease or even prevent such neurodegeneration altogether.
The present invention provides new phenyl oxazole and phenyl thiazole compounds useful for treating neurodegeneration and reperfusion injury of peripheral organs. The compounds of the invention inhibit the formation of reactive oxygen species in a mammal and are thereby useful for treating conditions and diseases which are believed to be induced by increased free radical production such as global and cerebral ischemia, Parkinson's disease, Alzheimer's disease, Down's syndrome, ALS and ischemia/reperfusion injury of peripheral organs.
Malamas, et al., U.S. Pat. No. 5,428,0478 disclose phenyl oxazoles useful for treating diseases of inflammation, allergic responses and arteriosclerosis while Panetta, et al., EP Application No. 677,517 teach benzylidene rhodanines to treat Alzheimer's disease.